It is well-known to use flow lines to convey various fluids from one location to another. Flow lines are used at virtually all stages of processing of fluids, including production facilities, storage facilities and processing facilities. Quite often the fluids are conveyed under pressure in pipeline systems, and it is not uncommon that the fluid conveyed by pipeline systems is hazardous due either to its toxicity, corrosiveness, flammability or the like. Despite the dangerous nature of such chemicals, modern technology relies heavily on their use in industry.
Pipelines are usually constructed of a plurality of pieces or sections joined together to form a continuous fluid communication pathway. In such pipeline systems, it is well-known to use seals at the interfaces between joined pieces to prevent leakage of the fluid at the joint. Commonly these seals are in the form of gaskets interposed between the joined pieces at their interface with the gaskets carrying compressible seal rings. In some instances, isolation gaskets are used in critical service applications to electrically isolate adjacent pieces of the pipeline.
Wherever industry is practiced, there is always the risk of fire, and this risk is compounded where flammable or explosive fluids are conveyed by pipeline systems. In the event of a fire at a facility using such pipeline facilities, the heat generated by the fire can stress the pipeline system due to the thermal expansion of the pieces which form the pipeline. For example, where steel piping is used, thermal expansion due to extremely elevated temperatures can cause separation of the pipe segments at their flange joints. When this occurs, the fluid conveyed by the pipeline can readily leak into the environment. Not only is there a risk that workers and equipment will become exposed to such fluids or their vapors, but also, where the fluids are flammable or explosive, leakage at separation gaps between the pipeline segments can allow a fire to be fed by the fluid. For example, at oil refineries, a fire poses substantial risk since leakage of the oil or gas at the refinery will provide additional fuel for the fire making it extremely difficult if not impossible to contain the fire. Due to the extreme flammability of these materials, it is sometimes impossible to evacuate workers from the site when a fire occurs.
It has been recognized that an interface gasket may be employed in order to help reduce the risk of leakage from thermal separation of pipeline sections when subjected to elevated temperature such as occur in fire situations. An example of such is shown in U.S. patent application No. 801,770 entitled FIREPROOF GASKET FOR PIPE FLANGES. In this disclosure, a gasket in the shape of a Belleville spring washer is disclosed, and the surfaces of this gasket are provided with annular seals. The gasket is compressed between the flanges of joined pipe segments in order to apply this seal therebetween. Should the pipe segments be separated by thermal expansion or stress on the system, the gaskets can flex to compensate for the separation gap.
While not disclosing gaskets for fireproof purposes, other expandable gaskets are known. One example of an expandable gasket is shown in U.S. Pat. No. 1,825,962 issued 6 Oct. 1931 to Laird, and another example of an expandable gasket is shown in U.S. Pat. No. 1,965,273 issued 3 Jul. 1934 to Wilson. The gasket taught in the Laird patent is an annular gasket element formed of relatively soft metal configured in a frustoconical shape. This metallic washer is simply compressed between the flanges of a pair of joined pipe sections. Wilson discloses similar frustoconical metallic gaskets but includes a variety of configurations of auxiliary webs to enhance the seal between the flanges of two pipe sections.
Present day fireproof gaskets commonly employed in the connection of pipes and installations subject to a high degree of fire hazard employ old and traditional approaches using spiral wound metallic gaskets or gaskets made of graphite based material. While there is no doubt that these present day fireproof gaskets are made of a material or materials capable of withstanding the elevated temperatures encountered in fire situations, they are still subjected to leakage at the pipe section interfaces when separation gaps are caused by thermal expansion.
Heretofore, it has also been known to use intumescent material in applications where there is the hazard of fire. Such intumescent material maybe a graphite catalyzed polyurethane, silicone, polyester or other such materials which expand in volume under the influence of elevated temperatures. This material can be compounded to activate at different temperatures so that it may only become activated under the influence of a fire. The primary use of such intumescent material has been to surround pipes and cables where they pass through walls or fire protected compartments in order to reduce or prevent the passage of smoke, fumes or fire through or around the pipes or cables. One such product is a pipe sleeve marketed by Fire Store, Ltd.
Despite the development of different gasket configurations, there remains a need for improved protective seals which can be used in conjunction with fluid flow lines, such as pipeline systems. There is a need for such a protective seal that will activate at elevated temperatures caused by a fire condition and which will directly act on the interface between joined pieces in a flow line in order to reduce or eliminate leakage due to separation gaps between those pieces resulting from thermal expansion. There is a further need for such seals that can be originally installed when pipeline systems are constructed or which can be inserted as retro-fit elements on such pipeline systems.